Chemical Degradation of Membrane Polymer Model Compounds under Simulated Fuel Cell Conditions

Aluminum was considered a good candidate material for bipolar plates of the polymer electrolyte membrane (PEM) fuel cells due to its low cost, light weight, high strength and good manufacturability. But there were problems of both chemical and electrochemical corrosions in the PEM fuel cell operating environment. The major goals of this research are to find proper physical vapor deposition (PVD) coating materials which would enhance surface properties by making significant improvements on corrosion resistance and electrical conductivity at a reasonable cost. Several coating materials had been studied to analyze their corrosion resistance improvement. The corrosion rates of all materials were tested in a simulated fuel cell environment. The linear polarization curve of electrochemical method measured by potentiostat instrument was employed to determine the corrosion current. Results of the corrosion tests indicated that all of the coating materials had good corrosion resistance and were stable in the simulated fuel cell environment. The conductivities of the coated layers were better and the resistances changed very little after the corrosion test. At last, single fuel cells were made by each PVD coating material. Fuel cell tests were conducted to determine their performance w.r.t. that was made of graphite. The results of fuel cell tests indicated that metallic bipolar plates with PVD coating could be used in PEM fuel cells.

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The Effect of Cathode Pressure Perturbations on the Voltage Stability of a Simulated Fuel Cell Stack

ECS Transactions ◽

10.1149/06403.0681ecst ◽

2014 ◽

Vol 64 (3) ◽

pp. 681-688

Author(s):

M. Burkholder ◽

S. Litster

Keyword(s):

Fuel Cell ◽

Voltage Stability ◽

Fuel Cell Stack ◽

Simulated Fuel ◽

Pressure Perturbations

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Irradiation Effects of Paraffins as Polymer Model Compounds

ACS Symposium Series - Radiation Effects on Polymers ◽

10.1021/bk-1991-0475.ch027 ◽

1991 ◽

pp. 442-456

Author(s):

Tadao Seguchi

Keyword(s):

Polymer Model ◽

Irradiation Effects ◽

Model Compounds

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Modeling of Coupled Mechanical and Chemical Degradation of the Ionomer Membrane in Polymer Electrolyte Fuel Cells

ECS Meeting Abstracts ◽

10.1149/ma2018-01/32/1992 ◽

2018 ◽

Vol MA2018-01 (32) ◽

pp. 1992-1992

Author(s):

Mohamed El Hannach ◽

Ka Hung Wong ◽

Yadvinder Singh ◽

Narinder Singh Khattra ◽

Erik Kjeang

Keyword(s):

Fuel Cells ◽

Fuel Cell ◽

Operating Conditions ◽

Chemical Degradation ◽

Mechanical Degradation ◽

Oh Radicals ◽

List Type ◽

Hydrogen Fuel Cell ◽

Hydrogen Fuel ◽

Power Sources

The hydrogen fuel cell is a promising technology that supports the development of sustainable energy systems and zero emission vehicles. One of the key technical challenges for the use of fuel cells in the transportation sector is the high durability requirements 1–3. One of the key components that control the overall life time of a hydrogen fuel cell is the ionomer membrane that conducts the protons and allows the separation between the anode and the cathode. During fuel cell operation, the membrane is subjected to two categories of degradation: mechanical and chemical. These degradations lead to reduction in the performance, crossover of reactants between anode and cathode and ultimately total failure of the fuel cell. The mechanical degradation occurs when the membrane swells and shrinks under the variation of the local hydration level. This leads to fatigue of the ionomer structure and ultimately irreversible damage. However, under pure mechanical degradation the damage takes a very long time to occur 4,5. Sadeghi et al. 5 observed failure of the membrane after 20,000 of accelerated mechanical stress testing. This translates into a longer lifetime in comparison to what is observed in field operation 6. The chemical degradation on the other hand is caused by the presence of harmful chemicals such as OH radicals that attack the side chains and the main chains of the ionomer 7,8. Such attacks weaken the structural integrity of the membrane and make it prone to severe mechanical damage. Hence understanding the effect of combining both categories of membrane degradation is the key to accurate prediction of the time to failure of the fuel cell. In this work we propose a novel model that represents accurately the structural properties of the membrane and couples the chemical and the mechanical degradations to estimate when the ultimate failure is initiated. The model is based on a network of agglomerated fibrils corresponding to the basic building block of the membrane structure 9–11. The mechanical and chemical properties are defined for each fibril and probability functions are used to evaluate the likelihood of a fibril to break under certain operating conditions. The description of the fundamentals behind the approach will be presented. Two set of simulations will be presented and discussed. The first one corresponding to standard testing scenarios that were used to validate the model. The second set of results will highlight the impact of coupling both degradation mechanisms on the estimation of the failure initiation time. The main strengths of the model and the future development will be discussed as well. T. Sinigaglia, F. Lewiski, M. E. Santos Martins, and J. C. Mairesse Siluk, Int. J. Hydrogen Energy, 42, 24597–24611 (2017). T. Jahnke et al., J. Power Sources, 304, 207–233 (2016). P. Ahmadi and E. Kjeang, Int. J. Energy Res., 714–727 (2016). X. Huang et al., J. Polym. Sci. Part B Polym. Phys., 44, 2346–2357 (2006). A. Sadeghi Alavijeh et al., J. Electrochem. Soc., 162, F1461–F1469 (2015). N. Macauley et al., J. Power Sources, 336, 240–250 (2016). K. H. Wong and E. Kjeang, J. Electrochem. Soc., 161, F823–F832 (2014). K. H. Wong and E. Kjeang, ChemSusChem, 8, 1072–1082 (2015). P.-É. A. Melchy and M. H. Eikerling, J. Phys. Condens. Matter, 27, 325103–6 (2015). J. A. Elliott et al., Soft Matter, 7, 6820 (2011). L. Rubatat, G. Gebel, and O. Diat, Macromolecules, 37, 7772–7783 (2004).

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